EFCore执行Sql语句的方法：FromSql与ExecuteSqlCommand

前言

在EFCore中执行Sql语句的方法为：FromSql与ExecuteSqlCommand；在EF6中的为SqlQuery与ExecuteSqlCommand，而FromSql和SqlQuery有很大区别，FromSql返回值为IQueryable，因此为延迟加载的，可以与Linq扩展方法配合使用，但是有不少的坑(EFCore版本为1.1.0)，直接执行Sql语句的建议不要使用FromSql，但是EFCore中并没有提供SqlQuery方法，因此下面会贴出SqlQuery的实现代码供大家参考，以便在EFCore中能使用。

FromSql和ExecuteSqlCommand的使用

测试时使用了SqlServer2008和SqlServer Profiler进行Sql语句捕捉，EFCore的版本为1.1.0。

测试的Entity Model与DbContext

 

 

ExecuteSqlCommand

EFCore的ExecuteSqlCommand和EF6的一样，执行非查询的Sql语句：

1             var db = new MSSqlDBContext();
2             db.Database.ExecuteSqlCommand($"update {nameof(Person)} set name=@name where id=@id", new[] 
3             {
4                 new SqlParameter("name", "tom1"),
5                 new SqlParameter("id", 1),
6             });

 

FromSql

官方参考文档：https://docs.microsoft.com/en-us/ef/core/querying/raw-sql

简单使用

1             var db = new MSSqlDBContext();
2             var name = "tom";
3             var list = db.Set<Person>().FromSql($"select * from {nameof(Person)} where {nameof(name)}=@{nameof(name)} ", 
4                 new SqlParameter(nameof(name), name)).ToList();

生成的Sql：

exec sp_executesql N'select * from Person where name=@name 
',N'@name nvarchar(3)',@name=N'tom'

注意：

默认生成的为Person的Model，如果Select获取的字段中不包含Person中的某字段就会抛异常了，例如：下面的语句只获取name字段，并没有包含Person的其他字段，那么抛异常：The required column 'id' was not present in the results of a 'FromSql' operation.

db.Set<Person>().FromSql($"select name from {nameof(Person)} ").ToList();

那么改为：

db.Set<Person>().Select(l => l.name).FromSql($"select name from {nameof(Person)} ").ToList();

 

执行存储过程

1             var db = new MSSqlDBContext();
2             db.Set<Person>().FromSql("exec testproc @id", new SqlParameter("id", 1)).ToList();

生成的Sql：

exec sp_executesql N'exec testproc @id
',N'@id int',@id=1

 

与Linq扩展方法配合使用

1             var db = new MSSqlDBContext();
2             db.Set<Person>().FromSql($"select * from {nameof(Person)} where name=@name ", new SqlParameter("@name", "tom"))
3                 .Select(l => new { l.name, l.birthday }).ToList();

生成的Sql：

 

inner join + order by

1             var db = new MSSqlDBContext();
2              (from p in db.Set<Person>().FromSql($"select * from {nameof(Person)} ")
3              join a in db.Set<Address>().Where(l => true)
4              on p.addrid equals a.id
5              select new { p.id, p.name, a.fullAddress }).OrderBy(l => l.id).ToList();

生成的Sql：

 

left join + order by

1             var db = new MSSqlDBContext();
2              (from p in db.Set<Person>().FromSql($"select * from {nameof(Person)} ")
3              join a in db.Set<Address>().Where(l => true)
4              on p.addrid equals a.id into alist
5              from a in alist.DefaultIfEmpty()
6              select new { p.id, p.name, fullAddress = a == null ? null : a.fullAddress }).OrderBy(l => l.id).ToList();

生成的Sql：(生成的Sql很有问题，order by后面多了[p].[addrid]，而且生成的select的字段也是多了)

SELECT [p].[id], [p].[addrid], [p].[birthday], [p].[name], [t].[id], [t].[fullAddress], [t].[lat], [t].[lon]
FROM (
    select * from Person 
) AS [p]
LEFT JOIN (
    SELECT [l0].[id], [l0].[fullAddress], [l0].[lat], [l0].[lon]
    FROM [Address] AS [l0]
) AS [t] ON [p].[addrid] = [t].[id]
ORDER BY [p].[id], [p].[addrid]

将FromSql换成Where扩展方法试试：

1             (from p in db.Set<Person>().Where(l => true)
2              join a in db.Set<Address>().Where(l => true)
3              on p.addrid equals a.id into alist
4              from a in alist.DefaultIfEmpty()
5              select new { p.id, p.name, fullAddress = a == null ? null : a.fullAddress }).OrderBy(l => l.id).ToList();

EFCore生成的Sql（order by后面还是多了[addrid]，select的字段也是多了）：

SELECT [l].[id], [l].[addrid], [l].[birthday], [l].[name], [t].[id], [t].[fullAddress], [t].[lat], [t].[lon]
FROM [Person] AS [l]
LEFT JOIN (
    SELECT [l1].[id], [l1].[fullAddress], [l1].[lat], [l1].[lon]
    FROM [Address] AS [l1]
) AS [t] ON [l].[addrid] = [t].[id]
ORDER BY [l].[id], [l].[addrid]

而在EF6中生成的Sql，比EFCore的生成好多了：

SELECT 
    [Project1].[id] AS [id], 
    [Project1].[name] AS [name], 
    [Project1].[C1] AS [C1]
    FROM ( SELECT 
        [Extent1].[id] AS [id], 
        [Extent1].[name] AS [name], 
        CASE WHEN ([Extent2].[id] IS NULL) THEN CAST(NULL AS varchar(1)) ELSE [Extent2].[fullAddress] END AS [C1]
        FROM  [dbo].[Person] AS [Extent1]
        LEFT OUTER JOIN [dbo].[Address] AS [Extent2] ON [Extent1].[addrid] = [Extent2].[id]
    )  AS [Project1]
    ORDER BY [Project1].[id] ASC

结果说明

FromSql不能代替原来EF6的SqlQuery使用，而且结合Linq扩展方法使用的时候生成的Sql会存在一些问题(EFCore版本为：1.1.0)，那么为了能在EFCore中执行Sql查询语句，下面提供对SqlQuery方法的实现。

SqlQuery的实现

 

使用：

1             var db = new MSSqlDBContext();
2             string name = "tom";
3             var list = SqlQuery<PAModel>(db,
4                 $" select p.id, p.name, a.fullAddress, a.lat, a.lon " +
5                 $" from ( select * from {nameof(Person)} where {nameof(name)}=@{nameof(name)} ) as p " +
6                 $" left join {nameof(Address)} as a on p.addrid = a.id ",
7                 new[] { new SqlParameter(nameof(name), name) });

生成的Sql：

exec sp_executesql N' select p.id, p.name, a.fullAddress, a.lat, a.lon  from ( select * from Person where name=@name ) as p  left join Address as a on p.addrid = a.id ',N'@name nvarchar(3)',@name=N'tom'